The present invention relates to a phase adjusting apparatus for adjusting a relative phase between a paper sheet feeder and a printing apparatus in accordance with a paper feed state for the printing press in a sheet-fed printing press.
In a sheet-fed printing press, paper sheets stacked on a stack board are drawn by suction from an uppermost sheet by a sheet pick-up device one by one, and are fed onto a feedboard through a feeder board. Thereafter, the sheet is gripped and conveyed by grippers of a swing gripper. The sheet is subjected to printing while being gripped and conveyed by grippers of a plate cylinder of the printing apparatus.
In such a sheet-fed printing press, rotation of a motor is transmitted to a printing apparatus, and is then transmitted to the sheet pick-up device of the paper sheet feeder or a paper convey tape provided on the feeder board through a chain or a line shaft. If a rotational phase between the paper sheet feeder and the printing apparatus is fixed at a given value, when the tape is extended or is slid along a paper sheet, the sheet cannot be fed to the printing apparatus at a predetermined timing. Thus, grippers may fail to grip the sheet or may unsatisfactorily grip it, resulting in printing error or trouble which causes the printing press to be stopped. In order to prevent this, a phase adjusting apparatus cooperating with elongated holes and bolts is provided at any location in a driving system between the printing apparatus and the paper sheet feeder. If an abnormality is found upon observation of the gripping state of the grippers, the sheet feed timing of the paper sheet feeder is advanced or delayed with respect to the printing apparatus.
However, the conventional phase adjusting apparatus cannot be operated during operation of a printing press, and adjustment must be performed after the printing press is stopped. Therefore, workability is degraded, and an operator cannot perform adjustment while observing the gripping state of the grippers. Therefore, appropriate adjustment cannot be achieved the first time, and readjustment must be repeated several times. Therefore, an idle time is prolonged, and the number of wasted paper sheets is increased. Another conventional phase adjusting apparatus which can be adjusted during the operation of the printing press and adopts planetary gears in a driving system between the printing apparatus and the paper sheet feeder is proposed. However, this apparatus has a complicated structure, and a distance between the shafts of the gears must be changed. Therefore, backlash of the gears is increased, thus unstabilizing phase.